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      Overexpression of the rhodanese PspE, a single cysteine-containing protein, restores disulphide bond formation to an Escherichia coli strain lacking DsbA.

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          Abstract

          Escherichia coli uses the DsbA/DsbB system for introducing disulphide bonds into proteins in the cell envelope. Deleting either dsbA or dsbB or both reduces disulphide bond formation but does not entirely eliminate it. Whether such background disulphide bond forming activity is enzyme-catalysed is not known. To identify possible cellular factors that might contribute to the background activity, we studied the effects of overexpressing endogenous proteins on disulphide bond formation in the periplasm. We find that overexpressing PspE, a periplasmic rhodanese, partially restores substantial disulphide bond formation to a dsbA strain. This activity depends on DsbC, the bacterial disulphide bond isomerase, but not on DsbB. We show that overexpressed PspE is oxidized to the sulphenic acid form and reacts with substrate proteins to form mixed disulphide adducts. DsbC either prevents the formation of these mixed disulphides or resolves these adducts subsequently. In the process, DsbC itself gets oxidized and proceeds to catalyse disulphide bond formation. Although this PspE/DsbC system is not responsible for the background disulphide bond forming activity, we suggest that it might be utilized in other organisms lacking the DsbA/DsbB system.

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          Author and article information

          Journal
          Mol. Microbiol.
          Molecular microbiology
          Wiley-Blackwell
          1365-2958
          0950-382X
          Sep 2012
          : 85
          : 5
          Affiliations
          [1 ] Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA.
          Article
          NIHMS391099
          10.1111/j.1365-2958.2012.08157.x
          3429705
          22809289
          1a51f0c7-5771-4219-a9e0-5e43e2d89492
          History

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